feat(init): cache output for faster shell startup

CLAUDE.md

@@ -112,7 +112,7 @@ cmd_editor() → resolve_target() → load_editor_adapter() → editor_open()
 
 **`.gtrconfig`**: Team-shared config using gitconfig syntax, parsed via `git config -f`. Keys map differently from git config (e.g., `gtr.copy.include` → `copy.include`, `gtr.hook.postCreate` → `hooks.postCreate`). See the .gtrconfig Key Mapping table in README or `docs/configuration.md`.
 
-**`init` command**: Outputs shell functions for `gtr cd <branch>` navigation. Users add `eval "$(git gtr init bash)"` to their shell rc file.
+**`init` command**: Outputs shell functions for `gtr cd <branch>` navigation. Output is cached to `~/.cache/gtr/` and auto-invalidates on version change. Users add `eval "$(git gtr init bash)"` to their shell rc file, or source the cache file directly for faster startup.
 
 **`clean --merged`**: Removes worktrees whose PRs/MRs are merged. Auto-detects GitHub (`gh`) or GitLab (`glab`) from the `origin` remote URL. Override with `gtr.provider` config for self-hosted instances.
 

README.md

@@ -101,7 +101,7 @@ git gtr run my-feature npm test # Run tests
 
 # Navigate to worktree
 gtr cd                          # Interactive picker (requires fzf + shell integration)
-gtr cd my-feature               # Requires: eval "$(git gtr init bash)"
+gtr cd my-feature               # Requires shell integration (see below)
 cd "$(git gtr go my-feature)"   # Alternative without shell integration
 
 # List all worktrees
@@ -214,15 +214,27 @@ cd "$(git gtr go 1)"             # Navigate to main repo
 **Tip:** For easier navigation, use `git gtr init` to enable `gtr cd`:
 
 ```bash
-# Add to ~/.bashrc or ~/.zshrc (one-time setup)
-eval "$(git gtr init bash)"
+# Bash (add to ~/.bashrc)
+_gtr_init="${XDG_CACHE_HOME:-$HOME/.cache}/gtr/init-gtr.bash"
+[[ -f "$_gtr_init" ]] || eval "$(git gtr init bash)"
+source "$_gtr_init" 2>/dev/null; unset _gtr_init
+
+# Zsh (add to ~/.zshrc)
+_gtr_init="${XDG_CACHE_HOME:-$HOME/.cache}/gtr/init-gtr.zsh"
+[[ -f "$_gtr_init" ]] || eval "$(git gtr init zsh)"
+source "$_gtr_init" 2>/dev/null; unset _gtr_init
+
+# Fish (add to ~/.config/fish/config.fish)
+git gtr init fish | source
 
 # Then navigate with:
 gtr cd                # Interactive worktree picker (requires fzf)
 gtr cd my-feature
 gtr cd 1
 ```
 
+The cache auto-regenerates on first run and auto-invalidates when git-gtr is updated. To force-regenerate: `rm -rf ~/.cache/gtr`
+
 With [fzf](https://github.com/junegunn/fzf) installed, `gtr cd` (no arguments) opens a command palette with git log preview and keybindings: `ctrl-e` editor, `ctrl-a` AI, `ctrl-d` delete, `ctrl-y` copy, `ctrl-r` refresh.
 
 > **Note:** If `gtr` conflicts with another command (e.g., GNU `tr` from coreutils), use `--as` to pick a different name:

bin/git-gtr

@@ -110,7 +110,7 @@ main() {
       local _shell_name
       _shell_name="$(basename "${SHELL:-bash}")"
       log_error "'cd' requires shell integration (subprocesses cannot change your shell's directory)"
-      log_info "Set up with: eval \"\$(git gtr init $_shell_name)\""
+      log_info "Set up with: eval \"\$(git gtr init $_shell_name)\"  (output is cached for fast startup)"
       log_info "Then use:    gtr cd [<branch>]"
       exit 1
       ;;

lib/commands/help.sh

@@ -103,6 +103,7 @@ Usage: git gtr go <branch>
 Prints the absolute path to the specified worktree. Useful for navigation
 with cd or for scripting. For direct cd support, use shell integration:
   eval "$(git gtr init bash)"    # then: gtr cd <branch>
+  (output is cached automatically for fast startup)
 
 Special:
   Use '1' for the main repo root: git gtr go 1
@@ -345,18 +346,26 @@ Usage: git gtr init <shell> [--as <name>]
 Generates shell functions for enhanced features like 'gtr cd <branch>'
 which changes directory to a worktree. Add to your shell configuration.
 
+Output is cached to ~/.cache/gtr/ for fast shell startup (~1ms vs ~60ms).
+The cache auto-invalidates when git-gtr is updated. To force-regenerate:
+  rm -rf ~/.cache/gtr
+
 Supported shells: bash, zsh, fish
 
 Options:
   --as <name>   Set custom function name (default: gtr)
                 Useful if 'gtr' conflicts with another command (e.g., GNU tr)
 
-Setup:
+Setup (sources cached output directly for fast startup):
   # Bash (add to ~/.bashrc)
-  eval "$(git gtr init bash)"
+  _gtr_init="${XDG_CACHE_HOME:-$HOME/.cache}/gtr/init-gtr.bash"
+  [[ -f "$_gtr_init" ]] || eval "$(git gtr init bash)"
+  source "$_gtr_init" 2>/dev/null; unset _gtr_init
 
   # Zsh (add to ~/.zshrc)
-  eval "$(git gtr init zsh)"
+  _gtr_init="${XDG_CACHE_HOME:-$HOME/.cache}/gtr/init-gtr.zsh"
+  [[ -f "$_gtr_init" ]] || eval "$(git gtr init zsh)"
+  source "$_gtr_init" 2>/dev/null; unset _gtr_init
 
   # Fish (add to ~/.config/fish/config.fish)
   git gtr init fish | source
@@ -558,7 +567,8 @@ SETUP & MAINTENANCE:
   init <shell> [--as <name>]
          Generate shell integration for cd support (bash, zsh, fish)
          --as <name>: custom function name (default: gtr)
-         Usage: eval "$(git gtr init bash)"
+         Output is cached for fast startup (auto-invalidates on update)
+         See git gtr help init for recommended setup
          With fzf: 'gtr cd' opens a command palette (preview, editor, AI, delete)
 
   version

lib/commands/init.sh

@@ -50,33 +50,50 @@ cmd_init() {
     return 1
   fi
 
+  # Resolve generator function
+  local generator
   case "$shell" in
-    bash)
-      _init_bash | sed "s/__FUNC__/$func_name/g"
-      ;;
-    zsh)
-      _init_zsh | sed "s/__FUNC__/$func_name/g"
-      ;;
-    fish)
-      _init_fish | sed "s/__FUNC__/$func_name/g"
-      ;;
-    "")
-      show_command_help
-      ;;
+    bash) generator="_init_bash" ;;
+    zsh)  generator="_init_zsh" ;;
+    fish) generator="_init_fish" ;;
+    "")   show_command_help; return 0 ;;
     *)
       log_error "Unknown shell: $shell"
       log_error "Supported shells: bash, zsh, fish"
       log_info "Run 'git gtr init --help' for usage"
       return 1
       ;;
   esac
+
+  # Generate output (cached to ~/.cache/gtr/, auto-invalidates on version change)
+  local cache_dir="${XDG_CACHE_HOME:-$HOME/.cache}/gtr"
+  local cache_file="$cache_dir/init-${func_name}.${shell}"
+  local cache_stamp="# gtr-cache: version=${GTR_VERSION:-unknown} func=$func_name shell=$shell"
+
+  # Return cached output if version matches
+  if [ -f "$cache_file" ]; then
+    local first_line
+    first_line="$(head -1 "$cache_file")"
+    if [ "$first_line" = "$cache_stamp" ]; then
+      tail -n +2 "$cache_file"
+      return 0
+    fi
+  fi
+
+  # Generate, cache, and output
+  local output
+  output="$("$generator" | sed "s/__FUNC__/$func_name/g")"
+  mkdir -p "$cache_dir"
+  printf '%s\n%s\n' "$cache_stamp" "$output" > "$cache_file"
+  printf '%s\n' "$output"
 }
 
 _init_bash() {
   cat <<'BASH'
-# git-gtr shell integration
+# git-gtr shell integration (output is cached to ~/.cache/gtr/)
 # Add to ~/.bashrc:
 #   eval "$(git gtr init bash)"
+# Faster: source the cache file directly (see git gtr help init)
 
 __FUNC__() {
   if [ "$#" -gt 0 ] && [ "$1" = "cd" ]; then
@@ -179,9 +196,10 @@ BASH
 
 _init_zsh() {
   cat <<'ZSH'
-# git-gtr shell integration
+# git-gtr shell integration (output is cached to ~/.cache/gtr/)
 # Add to ~/.zshrc:
 #   eval "$(git gtr init zsh)"
+# Faster: source the cache file directly (see git gtr help init)
 
 __FUNC__() {
   emulate -L zsh

tests/init.bats

@@ -5,6 +5,13 @@ load test_helper
 
 setup() {
   source "$PROJECT_ROOT/lib/commands/init.sh"
+  # Isolate cache to temp dir so tests don't pollute ~/.cache or each other
+  export XDG_CACHE_HOME="$BATS_TMPDIR/gtr-init-cache-$$"
+  export GTR_VERSION="test"
+}
+
+teardown() {
+  rm -rf "$BATS_TMPDIR/gtr-init-cache-$$"
 }
 
 # ── Default function name ────────────────────────────────────────────────────
@@ -219,3 +226,63 @@ setup() {
   [[ "$output" == *"command git gtr"* ]]
   [[ "$output" == *"git gtr list --porcelain"* ]]
 }
+
+# ── caching (default behavior) ──────────────────────────────────────────────
+
+@test "init creates cache file and returns output" {
+  local cache_dir="$BATS_TMPDIR/gtr-cache-test-$$"
+  XDG_CACHE_HOME="$cache_dir" GTR_VERSION="9.9.9" run cmd_init zsh
+  [ "$status" -eq 0 ]
+  [[ "$output" == *"gtr()"* ]]
+  [ -f "$cache_dir/gtr/init-gtr.zsh" ]
+  rm -rf "$cache_dir"
+}
+
+@test "init returns cached output on second call" {
+  local cache_dir="$BATS_TMPDIR/gtr-cache-test-$$"
+  # First call: generates and caches
+  XDG_CACHE_HOME="$cache_dir" GTR_VERSION="9.9.9" run cmd_init bash
+  [ "$status" -eq 0 ]
+  local first_output="$output"
+  # Second call: reads from cache
+  XDG_CACHE_HOME="$cache_dir" GTR_VERSION="9.9.9" run cmd_init bash
+  [ "$status" -eq 0 ]
+  [ "$output" = "$first_output" ]
+  rm -rf "$cache_dir"
+}
+
+@test "cache invalidates when version changes" {
+  local cache_dir="$BATS_TMPDIR/gtr-cache-test-$$"
+  # Generate with version 1.0.0
+  XDG_CACHE_HOME="$cache_dir" GTR_VERSION="1.0.0" run cmd_init zsh
+  [ "$status" -eq 0 ]
+  # Check cache stamp
+  local stamp
+  stamp="$(head -1 "$cache_dir/gtr/init-gtr.zsh")"
+  [[ "$stamp" == *"version=1.0.0"* ]]
+  # Regenerate with version 2.0.0
+  XDG_CACHE_HOME="$cache_dir" GTR_VERSION="2.0.0" run cmd_init zsh
+  [ "$status" -eq 0 ]
+  stamp="$(head -1 "$cache_dir/gtr/init-gtr.zsh")"
+  [[ "$stamp" == *"version=2.0.0"* ]]
+  rm -rf "$cache_dir"
+}
+
+@test "cache uses --as func name in cache key" {
+  local cache_dir="$BATS_TMPDIR/gtr-cache-test-$$"
+  XDG_CACHE_HOME="$cache_dir" GTR_VERSION="9.9.9" run cmd_init bash --as myfn
+  [ "$status" -eq 0 ]
+  [[ "$output" == *"myfn()"* ]]
+  [ -f "$cache_dir/gtr/init-myfn.bash" ]
+  rm -rf "$cache_dir"
+}
+
+@test "cache works for all shells" {
+  local cache_dir="$BATS_TMPDIR/gtr-cache-test-$$"
+  for sh in bash zsh fish; do
+    XDG_CACHE_HOME="$cache_dir" GTR_VERSION="9.9.9" run cmd_init "$sh"
+    [ "$status" -eq 0 ]
+    [ -f "$cache_dir/gtr/init-gtr.${sh}" ]
+  done
+  rm -rf "$cache_dir"
+}